This paper reports previously obtained results concerning topographic change in a water area. Latitude-longitude components of positional data obtained from a GPS receiver were transformed to planar orthogonal coordinates, and vertical components of positional data were combined with depth data obtained from an echo sounder. A piecewise linear function defined on a triangular mesh represented a surface that fitted measurement results. This study applied those techniques to data obtained in measurement of November, 2021 and data obtained in measurement of September, 2022.